I have 2 ads on my main page 468x60 & 728x90 when i check impression for ad unit it shows less impression for 728x90 and more impression for 468x60 i believe impression is counted when the page loaded with adsense ads on it and all the time both ads are on the same page why is this?
see if this is your problem.. http://forums.digitalpoint.com/showthread.php?t=2228428 If not ... are they image ads ... if they are text ads... the number of ad units will change and hence the impression counts..